Verdi and Britten both considered writing operas based on King Lear, but eventually abandoned their plans. Contemporary composers have been less cautious: Aribert Reimann's Lear was written in the 1970s for the great baritone Dietrich Fischer-Dieskau, while 10 years ago the Finn Aulis Sallinen produced his Kuningas Lear. Now it's Alexander Goehr's turn, using a text extracted entirely from Shakespeare's play and taking a title from the final scene.

Goehr has promised this will be his final opera, ending what began in 1967 with Arden Must Die, based on an anonymous 16th-century play with tenuous Shakespearian connections. Here, though, Shakespeare looms too large, for by insisting on the original text Goehr gives himself problems. The speeches in Lear were meant to be spoken not sung, and the wrought arioso of Goehr's vocal writing is no substitute for their meaning and expressive power.

The text, selected with the help of the late Frank Kermode, is ordered into 24 short scenes, aimed at focusing the drama more closely on Lear and Gloucester. But despite the holier-than-thou attitude to their purity, the extracts are sometimes used out of sequence in the preludes and ritornelli Goehr creates. Dramatically, it's a strange mix. Japanese Noh plays are a major influence, with the nine singers on stage throughout and the roles of Cordelia and the Fool doubled, but the use of the choral ritornellli to comment on the action seems to come more from Brecht. The brassy soundworld of the chamber orchestra, with its military-band echoes, emphasises the Weimar connection, too, and the best portions of the score – the ditties for the Fool – hark back to Weill and Eisler, if without their melodic distinction.

The narrative thread is sometimes so elusive and the dramatic trajectory so weak that Promised End seems more like a commentary on the play than an operatic version of it, and presupposes far too much knowledge of the original. James Conway's stylish production for English Touring Opera, with striking designs by Adam Wiltshire, does what it can to make the story clear and, guided by Ryan Wigglesworth's lucid conducting, the cast try to make something believable out of characters who seem scarcely defined. Though Lina Markeby does create an impression as the Fool/Cordelia, even Roderick Earle's Lear and Nigel Robson's Gloucester aren't really three-dimensional, and the massive emotional weight of Shakespeare's tragedy is not to be felt anywhere.